The technology of the present disclosure relates to an optical scanning device and an image forming apparatus including the same.
In the related art, there has been known an optical scanning device mounted in an electrophotographic image forming apparatus. The optical scanning device emits light beams corresponding to image data at a predetermined writing timing, thereby exposing a photosensitive drum.
The optical scanning device includes a light source, a rotating polygon mirror that deflects light beams emitted from the light source and converts the light beams into scanning light, an image forming lens that allows an image of the scanning light from the rotating polygon mirror to be formed on a photosensitive drum, and a synchronization detection sensor that outputs a signal serving as a reference of a writing timing of image data. The synchronization detection sensor is provided out of an effective scanning region (out of an image formation region) of the light beams.
The synchronization detection sensor outputs a synchronization signal to a control unit when the amount of the light beams received from the light source is equal to or more than a prescribed threshold value. The control unit controls the writing timing of the image data to the photosensitive drum based on a reception timing of the synchronization signal.
In the optical scanning device, there is a case where a setting unit is provided to switch and set a low resolution mode and a high resolution mode. When the high resolution mode is set, the pixel density of an image in a vertical direction is increased by increasing a rotation speed of the rotating polygon mirror. Even when the resolution becomes high and the pixel density in the vertical direction is increased, since a beam diameter of light beams on a drum surface is constant, image failure such as character blurring may occur. In this regard, there has been proposed a technology for preventing the occurrence of image failure by reducing the amount (laser power) of light beams.